Expandable intervertebral implant and associated surgical method

ABSTRACT

The present invention provides an expandable intervertebral implant, including: a superior member configured to engage a superior intervertebral body; an inferior member configured to engage an inferior intervertebral body; and an expansion mechanism disposed between the superior member and the inferior member configured to selectively adjust a separation of the superior member from the inferior member; wherein the expansion mechanism includes a proximal wedge structure and a distal wedge structure that are relatively translated between the superior member and the inferior member, wherein the proximal wedge structure and the distal wedge structure are each coupled to the superior member and the inferior member by a plurality of aligned and/or staggered (i.e. nested) track structures and rail structures.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present patent application/patent is a continuation-in-part (CIP) ofco-pending U.S. patent application Ser. No. 12/974,511, filed on Dec.21, 2010, and entitled “EXPANDABLE INTERVERTEBRAL IMPLANT AND ASSOCIATEDSURGICAL METHOD,” which claims the benefit of priority of U.S.Provisional Patent Application No. 61/293,997, filed on Jan. 11, 2010,and entitled “EXPANDABLE INTERVERTEBRAL BODY STABILIZATION DEVICES ANDASSOCIATED SURGICAL METHODS” and U.S. Provisional Patent Application No.61/296,932, filed on Jan. 21, 2010, and entitled “EXPANDABLEINTERVERTEBRAL BODY STABILIZATION DEVICES AND ASSOCIATED SURGICALMETHODS,” the contents of all of which are incorporated in full byreference herein.

FIELD OF THE INVENTION

The present invention relates generally to minimally-invasive,surgically-implantable spinal devices and systems. More specifically,the present invention relates to an expandable intervertebral implantthat is surgically implanted to, in-situ, distract, realign, and/orstabilize or fuse a portion of the spine of a patient in the treatmentof injury, disease, and/or degenerative condition. Exemplary indicationsinclude, but are not limited to, spinal stenosis, degenerative discdisease with a loss of disc height, disc herniation, spondylolisthesis,retrolisthesis, and disogenic back pain. This expandable intervertebralimplant may be surgically implanted via an open or, more preferably, aminimally-invasive surgical procedure. Advantageously, the expandableintervertebral implant has both a very small undeployed verticalcross-section and a very small undeployed horizontal footprint due tothe use of superior and inferior members that nest against one anotherin a novel manner.

BACKGROUND OF THE INVENTION

In various cases, it is desirable to restore the anatomic relationshipbetween various vertebral elements, thereby re-establishing spinalstability, by means other than conventional monolithic and/ormulti-piece interbody spacers. Typically, these devices require sizableworking channels, soft tissue disruption, nerve root retraction, andsignificant bone resection, thereby increasing the resulting stress onother vertebral elements. Further, morbidities associated with thesemore-invasive procedures include, but are not limited to, greater bloodloss, longer recovery, and increased risk of surgical site infection.

In such cases, the use of an alternative intervertebral implant,especially one compatible with minimally-invasive surgical techniques,is desirable. An intervertebral implant that expands in-situ would allowimplantation without the iatrogenic insult that is commonly associatedwith the implantation of conventional monolithic and/or multi-pieceinterbody spacers in a minimally-invasive manner. However, no suchalternative devices or systems are currently available, at least not anythat are adequate.

BRIEF SUMMARY OF THE INVENTION

In various exemplary embodiments, the present invention provides anexpandable intervertebral implant that is selectively disposed in theintervertebral space and deployed, thereby in-situ distracting,realigning, and/or stabilizing or fusing a portion of the spine of apatient in the treatment of injury, disease, and/or degenerativecondition. The expandable intervertebral implant includes a superiormember and an inferior member, each of which has a partially orsubstantially wedge or prismatic shape and a partially or substantiallyconvex or other-shaped surface that is suitable for engaging thesubstantially concave surfaces of the associated bony superior andinferior intervertebral endplates. Optionally, the superior member andthe inferior member are each thinner at the leading edge of theexpandable intervertebral implant than they are at the trailing edge ofthe expandable intervertebral implant, such that insertion into theintervertebral space may be aided, although this is not a requirementand the expandable intervertebral implant may have a uniform thickness,when undeployed, from the leading edge to the trailing edge. For similarreasons, the leading edge of the both the superior member and theinferior member may have a knifed or rounded shape. Once disposed in theintervertebral space, the expandable intervertebral implant is actuatedand deployed, with the superior member and the inferior member movingapart from one another, seating against the associated intervertebralendplates, and distracting, realigning, and/or stabilizing them to adesired degree. In order to ensure that the expandable intervertebralimplant is held securely in the intervertebral space, the externalsurface of each of the superior member and the inferior member isprovided with a plurality of ridges or other friction structures,providing purchase with the associated intervertebral endplates.

When undeployed, the superior member and the inferior member areconfigured such that they nest against one another, thereby providingthe undeployed expandable intervertebral implant with the smallestpossible form factor for insertion through the skin and musculature ofthe patient and into the intervertebral space. In the exemplaryembodiment provided, this is accomplished via the use of cut-awaysections associated with the superior member and the inferior member,not unlike a tongue-in-groove joint assembly. The combined total heightof the superior member and the inferior member when nested together inthe undeployed state is less than the sum of the heights of the superiormember and the inferior member individually. This is accomplished via aplurality of nesting ramp structures and/or other angled surfacesassociated with the superior member and/or the inferior member thatselectively cause distraction/separation of the superior member and theinferior member via interaction with a translating wedge structure.These various ramp structures are offset (i.e. staggered) in such amanner that the form factor of the expandable intervertebral implant isminimized when undeployed.

In one exemplary embodiment, the present invention provides anexpandable intervertebral implant, including: a superior memberconfigured to engage a superior intervertebral body; an inferior memberconfigured to engage an inferior intervertebral body; and an expansionmechanism disposed between the superior member and the inferior memberconfigured to selectively adjust a separation of the superior member andthe inferior member. The expansion mechanism includes a wedge structurethat is translated between the superior member and the inferior member.The expansion mechanism also includes a screw that is coupled to thewedge structure and causes the wedge structure to translate whenrotated. One or more of the superior member and the inferior memberinclude a ramp structure on their opposed faces. Interaction of thewedge structure and the ramp structure of the one or more of thesuperior member and the inferior member as the wedge structure istranslated causes adjustment of the separation of the superior memberand the inferior member. The superior member is coupled to the inferiormember through the wedge structure and the ramp structure of the one ormore of the superior member and the inferior member. Optionally, thesuperior member is coupled to the inferior member via a track (i.e.channel) and rail system. The expansion mechanism disposed between thesuperior member and the inferior member may also be configured toselectively translate the superior member with respect to the inferiormember.

In another exemplary embodiment, the present invention provides anexpandable intervertebral implant, including: a superior memberconfigured to engage a superior intervertebral body; an inferior memberconfigured to engage an inferior intervertebral body; and an expansionmechanism disposed between the superior member and the inferior memberconfigured to selectively adjust a separation of the superior member andthe inferior member, wherein the expansion mechanism includes a wedgestructure that is translated between the superior member and theinferior member. The expansion mechanism also includes a screw that iscoupled to the wedge structure and causes the wedge structure totranslate when rotated. One or more of the superior member and theinferior member include a ramp structure on their opposed faces.Interaction of the wedge structure and the ramp structure of the one ormore of the superior member and the inferior member as the wedgestructure is translated causes adjustment of the separation of thesuperior member and the inferior member. The superior member is coupledto the inferior member through the wedge structure and the rampstructure of the one or more of the superior member and the inferiormember. Optionally, the superior member is coupled to the inferiormember via a track and rail system. The expansion mechanism disposedbetween the superior member and the inferior member may also beconfigured to selectively translate the superior member with respect tothe inferior member.

In a further exemplary embodiment, the present invention provides aspinal surgical method, including: providing an expandableintervertebral implant, including: a superior member configured toengage a superior intervertebral body; an inferior member configured toengage an inferior intervertebral body; and an expansion mechanismdisposed between the superior member and the inferior member configuredto selectively adjust a separation of the superior member and theinferior member; disposing the expandable intervertebral implant betweenthe superior intervertebral body and the inferior intervertebral body;and selectively adjusting the separation of the superior member and theinferior member, thereby selectively adjusting a distraction of thesuperior intervertebral body from the inferior intervertebral body. Theexpansion mechanism includes a wedge structure that is translatedbetween the superior member and the inferior member. The expansionmechanism also includes a screw that is coupled to the wedge structureand causes the wedge structure to translate when rotated. One or more ofthe superior member and the inferior member include a ramp structure ontheir opposed faces. Interaction of the wedge structure and the rampstructure of the one or more of the superior member and the inferiormember as the wedge structure is translated causes adjustment of theseparation of the superior member and the inferior member. The superiormember is coupled to the inferior member through the wedge structure andthe ramp structure of the one or more of the superior member and theinferior member. Optionally, the superior member is coupled to theinferior member via a track and rail system. The expansion mechanismdisposed between the superior member and the inferior member may also beconfigured to selectively translate the superior member with respect tothe inferior member.

In a still further exemplary embodiment, the present invention providesan expandable intervertebral implant, including: a superior memberconfigured to engage a superior intervertebral body; an inferior memberconfigured to engage an inferior intervertebral body; and an expansionmechanism disposed between the superior member and the inferior memberconfigured to selectively adjust a separation of the superior memberfrom the inferior member; wherein the expansion mechanism includes aproximal wedge structure and a distal wedge structure that arerelatively translated between the superior member and the inferiormember, wherein the proximal wedge structure and the distal wedgestructure are each coupled to the superior member and the inferiormember by a plurality of track structures and rail structures. One ormore track structures and rail structures associated with a top surfaceof the distal wedge structure are offset horizontally with respect toone or more track structures and rail structures associated with abottom surface of the distal wedge structure. One or more trackstructures and rail structures associated with a top surface of theproximal wedge structure are aligned horizontally with respect to one ormore track structures and rail structures associated with a bottomsurface of the proximal wedge structure. The expansion mechanism alsoincludes an actuation bolt that passes through the proximal wedgestructure and is coupled to the distal wedge structure and causes thewedge structures to relatively translate when rotated. The superiormember and the inferior member each include a plurality of rampstructures on their opposed faces. The superior member includes a rampstructure that engages the proximal wedge structure and a ramp structurethat engages the distal wedge structure. The inferior member includes aramp structure that engages the proximal wedge structure and a rampstructure that engages the distal wedge structure. The expandableintervertebral implant also includes a plurality of elongate armstructures protruding from the superior member and the inferior memberand engaging a corresponding recess of the other component.

In a still further exemplary embodiment, the present invention providesa surgical method including providing an expandable intervertebralimplant, including: a superior member configured to engage a superiorintervertebral body; an inferior member configured to engage an inferiorintervertebral body; and an expansion mechanism disposed between thesuperior member and the inferior member configured to selectively adjusta separation of the superior member from the inferior member; whereinthe expansion mechanism includes a proximal wedge structure and a distalwedge structure that are relatively translated between the superiormember and the inferior member, wherein the proximal wedge structure andthe distal wedge structure are each coupled to the superior member andthe inferior member by a plurality of track structures and railstructures. One or more track structures and rail structures associatedwith a top surface of the distal wedge structure are offset (i.e.staggered) horizontally with respect to one or more track structures andrail structures associated with a bottom surface of the distal wedgestructure. One or more track structures and rail structures associatedwith a top surface of the proximal wedge structure are alignedhorizontally with respect to one or more track structures and railstructures associated with a bottom surface of the proximal wedgestructure. Alternatively, one or more track structures and railstructures associated with a top surface of the proximal wedge structureare offset (i.e. staggered) horizontally with respect to one or moretrack structures and rail structures associated with a bottom surface ofthe proximal wedge structure. The expansion mechanism also includes anactuation bolt that passes through the proximal wedge structure and iscoupled to the distal wedge structure and causes the wedge structures torelatively translate when rotated. The superior member and the inferiormember each include a plurality of ramp structures on their opposedfaces. The superior member includes a ramp structure that engages theproximal wedge structure and a ramp structure that engages the distalwedge structure. The inferior member includes a ramp structure thatengages the proximal wedge structure and a ramp structure that engagesthe distal wedge structure. The expandable intervertebral implant alsoincludes a plurality of elongate arm structures protruding from thesuperior member and the inferior member and engaging a correspondingrecess of the other component.

BRIEF DESCRIPTION OF THE DRAWINGS

The expandable intervertebral implant of the present invention isillustrated and described herein with reference to the various drawings,in which like reference numbers are used to denote like devicecomponents, as appropriate, and in which:

FIG. 1 is a perspective view of one exemplary embodiment of theexpandable intervertebral implant of the present invention;

FIG. 2 is another perspective view of one exemplary embodiment of theexpandable intervertebral implant of the present invention;

FIG. 3 is a further perspective view of one exemplary embodiment of theexpandable intervertebral implant of the present invention;

FIG. 4 is a still further perspective view of one exemplary embodimentof the expandable intervertebral implant of the present invention;

FIG. 5 is a planar end view of one exemplary embodiment of theexpandable intervertebral implant of the present invention;

FIG. 6 is a still further perspective view of one exemplary embodimentof the expandable intervertebral implant of the present invention;

FIG. 7 is another planar end view of one exemplary embodiment of theexpandable intervertebral implant of the present invention;

FIG. 8 is a still further perspective view of one exemplary embodimentof the expandable intervertebral implant of the present invention;

FIG. 9 a is a partial perspective view of one exemplary embodiment ofthe expandable intervertebral implant of the present invention;

FIG. 9 b is another partial perspective view of one exemplary embodimentof the expandable intervertebral implant of the present invention;

FIG. 10 a is an exploded perspective view of one exemplary embodiment ofthe expandable intervertebral implant of the present invention;

FIG. 10 b is a partial exploded perspective view of one exemplaryembodiment of the expandable intervertebral implant of the presentinvention;

FIG. 10 c is another partial exploded perspective view of one exemplaryembodiment of the expandable intervertebral implant of the presentinvention;

FIG. 10 d is another exploded perspective view of one exemplaryembodiment of the expandable intervertebral implant of the presentinvention;

FIG. 10 e is a further partial exploded perspective view of oneexemplary embodiment of the expandable intervertebral implant of thepresent invention;

FIG. 11 is a planar side view of one exemplary embodiment of theexpandable intervertebral implant of the present invention;

FIG. 12 is another planar side view of one exemplary embodiment of theexpandable intervertebral implant of the present invention;

FIG. 13 is a further planar side view of one exemplary embodiment of theexpandable intervertebral implant of the present invention;

FIG. 14 is a still further perspective view of one exemplary embodimentof the expandable intervertebral implant of the present invention, alongwith a partial perspective view of one exemplary embodiment of theimplantation tool of the present invention;

FIG. 15 is a still further perspective view of one exemplary embodimentof the expandable intervertebral implant of the present invention, alongwith another partial perspective view of one exemplary embodiment of theimplantation tool of the present invention;

FIG. 16 is a still further perspective view of one exemplary embodimentof the expandable intervertebral implant of the present invention, alongwith a perspective view of one exemplary embodiment of the implantationtool of the present invention;

FIG. 17 is a still further perspective view of one exemplary embodimentof the expandable intervertebral implant of the present invention, alongwith another perspective view of one exemplary embodiment of theimplantation tool of the present invention;

FIGS. 18 a and 18 b are perspective views of an alternative exemplaryembodiment of the expandable intervertebral implant of the presentinvention in an unexpanded configuration;

FIGS. 19 a and 19 b are perspective views of an alternative exemplaryembodiment of the expandable intervertebral implant of the presentinvention in a partially or wholly expanded configuration;

FIG. 20 is a top/bottom planar view of an alternative exemplaryembodiment of the expandable intervertebral implant of the presentinvention;

FIGS. 21 a and 21 b are side planar views of an alternative exemplaryembodiment of the expandable intervertebral implant of the presentinvention in both unexpanded and partially or wholly expandedconfigurations;

FIGS. 22 a and 22 b are partial planar views of an alternative exemplaryembodiment of the expandable intervertebral implant of the presentinvention in both unexpanded and partially or wholly expandedconfigurations;

FIGS. 23 a and 23 b are perspective views of the superior and inferiormembers of an alternative exemplary embodiment of the expandableintervertebral implant of the present invention;

FIGS. 24 a and 24 b are additional perspective views of the superior andinferior members of an alternative exemplary embodiment of theexpandable intervertebral implant of the present invention;

FIG. 25 is an additional perspective view of the superior and inferiormembers of an alternative exemplary embodiment of the expandableintervertebral implant of the present invention;

FIG. 26 is a partial perspective view of the superior and inferiormembers of an alternative exemplary embodiment of the expandableintervertebral implant of the present invention in an assembledconfiguration (see also FIGS. 22 a and 22 b for partial planar views ofthe same);

FIGS. 27 a and 27 b are end planar views of the superior member and thedistal wedge structure of an alternative exemplary embodiment of theexpandable intervertebral implant of the present invention,respectively;

FIGS. 28 a and 28 b are perspective views of the superior and inferiormembers of an alternative exemplary embodiment of the expandableintervertebral implant of the present invention in an assembledconfiguration, both without and with the associated proximal and distalwedge structures in place, respectively;

FIGS. 29 a and 29 b are perspective views of the distal wedge structureof an alternative exemplary embodiment of the expandable intervertebralimplant of the present invention;

FIGS. 30 a and 30 b are side planar views of an alternative exemplaryembodiment of the expandable intervertebral implant of the presentinvention in both unexpanded and partially or wholly expandedconfigurations;

FIGS. 31 a and 31 b are end planar views of the proximal wedge structureof an alternative exemplary embodiment of the expandable intervertebralimplant of the present invention;

FIGS. 32 a and 32 b are perspective views of the proximal wedgestructure of an alternative exemplary embodiment of the expandableintervertebral implant of the present invention;

FIGS. 33 a and 33 b are perspective views of the actuation bolt of analternative exemplary embodiment of the expandable intervertebralimplant of the present invention;

FIG. 34 is a perspective view of the proximal wedge structure, thedistal wedge structure, and the actuation bolt of an alternativeexemplary embodiment of the expandable intervertebral implant of thepresent invention in an assembled configuration;

FIG. 35 is a perspective view of the implant inserter tool used toinsert an alternative exemplary embodiment of the expandableintervertebral implant of the present invention;

FIGS. 36 a and 36 b are perspective views of an end portion of theimplant inserter tool used to insert an alternative exemplary embodimentof the expandable intervertebral implant of the present invention, bothdisengaged from and engaged with the expandable intervertebral implant,respectively;

FIGS. 37 a and 37 b are perspective views of another end portion of theimplant inserter tool used to insert an alternative exemplary embodimentof the expandable intervertebral implant of the present invention, bothin unlocked and locked configurations, respectively;

FIGS. 38 a and 38 b are partial perspective views of another end portionof the implant inserter tool used to insert an alternative exemplaryembodiment of the expandable intervertebral implant of the presentinvention, both in unlocked and locked configurations, respectively;

FIG. 39 is a perspective view of another end portion of the implantinserter tool used to insert an alternative exemplary embodiment of theexpandable intervertebral implant of the present invention, highlightingthe engagement of the associated handle assembly;

FIG. 40 is a perspective view of the implant inserter tool used toinsert an alternative exemplary embodiment of the expandableintervertebral implant of the present invention, highlighting theengagement of the associated handle assembly;

FIGS. 41 a and 41 b are perspective views of another alternativeexemplary embodiment of the expandable intervertebral implant of thepresent invention in an unexpanded configuration;

FIG. 42 is a perspective view of the implant inserter tool used toinsert an alternative exemplary embodiment of the expandableintervertebral implant of the present invention, highlighting theengagement of the associated handle assembly and actuation handleassembly;

FIG. 43 is an exploded perspective view of another end portion of theimplant inserter tool used to insert alternative exemplary embodimentsof the expandable intervertebral implant of the present invention; and

FIGS. 44 a and 44 b are perspective views of the implant inserter toolused to insert alternative exemplary embodiments of the expandableintervertebral implant of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, in one exemplary embodiment, the present inventionprovides an expandable intervertebral implant 10 that is selectivelydisposed in the intervertebral space and deployed, thereby in-situdistracting, realigning, and/or stabilizing or fusing a portion of thespine of a patient in the treatment of injury, disease, and/ordegenerative condition. The expandable intervertebral implant 10includes a superior member 12 and an inferior member 14, each of whichhas a partially or substantially wedge or prismatic shape and apartially or substantially convex or other-shaped surface that issuitable for engaging the substantially concave surfaces of theassociated bony superior and inferior intervertebral endplates.Optionally, the superior member 12 and the inferior member 14 are eachthinner at the leading edge of the expandable intervertebral implant 10than they are at the trailing edge of the expandable intervertebralimplant 10, such that insertion into the intervertebral space may beaided, although this is not a requirement and the expandableintervertebral implant 10 may have a uniform thickness, when undeployed,from the leading edge to the trailing edge. For similar reasons, theleading edge of the both the superior member 12 and the inferior member14 may have a knifed or rounded shape. Once disposed in theintervertebral space, the expandable intervertebral implant 10 isactuated and deployed, with the superior member 12 and the inferiormember 14 moving apart from one another, seating against the associatedintervertebral endplates, and distracting, realigning, and/orstabilizing them to a desired degree. The mechanisms by which thishappens are described in greater detail herein below. This operation isanalogous to placing a jack under a car, positioning it appropriately,snugging it in the space beneath the car, and then jacking it up. Inorder to ensure that the expandable intervertebral implant 10 is heldsecurely in the intervertebral space, the external surface of each ofthe superior member 12 and the inferior member 14 is provided with aplurality of ridges 16 or other friction structures, providing purchasewith the associated intervertebral endplates. The overall dimensions ofthe expandable intervertebral implant 10 are on the order of severalmillimeters to tens of millimeters, such that a set of implantscontaining a series of incremental implant sizes can provide a heightexpansion range of 7-18 mm or more than 3-5 mm each, for example. Othersuitable dimensions may, of course, be utilized.

When undeployed, the superior member 12 and the inferior member 14 areconfigured such that they nest against one another, thereby providingthe undeployed expandable intervertebral implant 10 with the smallestpossible form factor (i.e. smallest possible undeployed verticalcross-section and smallest/shortest possible undeployed horizontalfootprint) for insertion through the skin and musculature of the patientand into the intervertebral space. In the exemplary embodimentillustrated in FIG. 1, this is accomplished via the use of cut-awaysections 18 and 20 associated with the superior member 12 and theinferior member 14.

By way of overview, the superior member 12 and the inferior member 14are actuated via the rotation of a screw 22 disposed through a housing24 located at the trailing edge of the expandable intervertebral implant10. This screw 22 is disposed along the central axis of the expandableintervertebral implant 10, between the superior member 12 and theinferior member 14. The screw 22 engages an internally-threaded wedgestructure 26 disposed between the superior member 12 and the inferiormember 14, selectively translating the wedge structure 26 along thecentral axis of the expandable intervertebral implant 10 with rotation.This translation causes the wedge structure 26 to interact with anassociated wedge shape or structure of the superior member 12 and/orinferior member 14, thereby forcing the superior member 12 and theinferior member 14 apart/together with translation of the wedgestructure 26. Preferably, the superior member 12 and the inferior member14 each include a track structure 28 and 30, thereby securely couplingthe superior member 12 to the inferior member 14 through the wedgestructure 26. The interaction of the wedge structure 26 with the wedgeshape or structure of the superior member 12 and/or inferior member 14during translation preferably causes the superior member 12 and theinferior member 14 to move apart/together while maintaining asubstantially parallel relationship. Alternatively, the superior member12 and the inferior member 14 may move apart with a predeterminedlordotic angle. The superior member 12 and the inferior member 14 maymove apart in a substantially-continuous fashion, or they may move apartin 0.5-mm or smaller increments, for example. In addition, theinteraction of the wedge structure 26, the superior member 12, and theinferior member 14 may be designed such that as the superior member 12and the inferior member 14 move apart, they also translate with respectto one another. This is helpful in, for example, ensuring that theplurality of ridges 16 or other friction structures are securely seatedin the bony material.

Another view of the expandable intervertebral implant 10 is provided inFIGS. 2 and 3. As is evident from FIGS. 2 and 3, the superior member 12and the inferior member 14 may each include one or more holes 32 orfenestrations to promote bony in-growth and fusion, as appropriate.Preferably, the superior member 12 and the inferior member 14 eachinclude a groove 34 and 36 in which the screw 22 is disposed. Thisnesting of the screw 22 within the superior member 12 and the inferiormember 14 provides the expandable intervertebral implant 10 with thesmallest possible form factor when undeployed, allowing the superiormember 12 and the inferior member 14 to collapse together, withoutinterference from the screw 22. The wedge structure 26 has acorresponding bore portion 38 (FIG. 3), through which the screw 22passes and which sits within the grooves 34 and 36 of the superiormember 12 and the inferior member 14, respectively. This configurationpermits the wedge structure 26 to translate smoothly along the centralaxis of the expandable intervertebral implant 10 with rotation of thescrew 22, distracting the superior member 12 and the inferior member 14,which holding the entire assembly in secure alignment. Along these samelines, the cut-away sections 18 and 20 of the superior member 12 and theinferior member 14, respectively, may form abutting surfaces 40perpendicular to the central axis of the expandable intervertebralimplant 10 that aide in holding the superior member 12 and the inferiormember 14 in alignment, despite their degree of deployment, by resistingrotation of the superior member 12 and the inferior member 14 withrespect to one another. Thus, the expandable intervertebral implant 10will expand upon deployment, as opposed to “clamshelling.” Also alongthese same lines, the track structures 28 and 30 of the superior member12 and the inferior member 14 are “dove-tailed” on one or both sides andengage corresponding channels 42 and 44 manufactured into the superiorand inferior surfaces of the wedge structure 26, again thereby securelycoupling the superior member 12 to the inferior member 14 through thewedge structure 26.

Referring to FIG. 4, the screw 22 preferably includes a keyed recess 46for receiving a driver, such as a hexalobular driver, by which the screw22 is rotated to translate the wedge structure 26. The housing 24includes a plurality of recesses 48 or the like for receiving aholding/placement tool. As is described in greater detail herein below,the driver and holding/placement tool may be incorporated into oneassembly, such that the expandable intervertebral implant 10 may begrasped, positioned, expanded, and released in a series of simple steps,by a single surgeon, using a single tool. As is also illustrated in FIG.4, the housing 24 may include a cylindrical recess 50 that is configuredto substantially contain the head of the screw 22, again reducing theoverall footprint of the expandable intervertebral implant 10.

FIG. 5 illustrates the cross-sectional footprint of the expandableintervertebral implant 10 along its central axis, demonstrating how thesuperior member 12 and the inferior member 14 nest with one anotherabout the screw 22 during implantation. FIG. 6 illustrates theexpandable intervertebral implant 10 in an only partially-deployedstate, while FIG. 7 illustrates the cross-sectional footprint of theexpandable intervertebral implant 10 along its central axis,demonstrating how the superior member 12 and the inferior member 14expand away from one another about the screw 22 and wedge structure 26during actuation and deployment. As is illustrated clearly in FIGS. 5and 7, the screw 22 may be cannulated, and a have a bore 52 passingthrough it along the central axis of the expandable intervertebralimplant 10. This cannulation aides in the placement of the expandableintervertebral implant 10 over a guide-wire or the like.

Referring to FIG. 8, it may be seen that the track structures 28 and 30of the superior member 12 and the inferior member 14, respectively, areoffset (i.e. staggered) from one another relative to the central axis ofthe expandable intervertebral implant 10 such that they sit side-by-sidewhen the expandable intervertebral implant 10 is un-depolyed, therebymaking the assembly as compact as possible. This also allows the trackstructures 28 and 30 of the superior member 12 and the inferior member14 to be longer (versus vertically aligned tracks 28 and 30), therebypermitting the wedge structure 26 of a fully contracted (i.e. fullyunexpanded) implant 10 to be disposed within the horizontal footprint ofthe superior member 12 and the inferior member 14 while maintainingminimum wedge translation (i.e. travel) length requirements to effectthe required distraction of the implant 10. Again, this makes theassembly as compact as possible, with the smallest possible undeployedvertical cross-section and the smallest/shortest possible undeployedhorizontal footprint. Accordingly, the channels 42 and 44 manufacturedinto the superior and inferior surfaces of the wedge structure 26,respectively, are also offset from one another relative to the centralaxis of the expandable intervertebral implant 10. FIG. 8 alsoillustrates the interaction of the slopes of the wedge structure 26 and,in this exemplary embodiment, the superior member 12. Again, theinteraction of the wedge structure 26 with the wedge shape or structureof the superior member 12 and/or inferior member 14 during translationpreferably causes the superior member 12 and the inferior member 14 tomove apart/together while maintaining a substantially parallelrelationship.

Referring to FIGS. 9 a and 9 b, the screw 22 includes a head portion 54that selectively sits within the cylindrical recess 50 of the housing 24and a threaded portion 56 that passes through the housing 24 to engagethe wedge structure 26. When properly positioned, the head portion 54 ofthe screw 22 sits flush with the exterior surface of the expandableintervertebral implant 10 and does not protrude. Preferably, the backside of the head portion 54 of the screw 22 includes a plurality ofteeth 58 or the like that frictionally engage the screw 22 with acorresponding plurality of teeth 60 or the like manufactured into theexposed floor of the cylindrical recess 50 of the housing 24. Thisratcheting or spiral jaw clutch mechanism aides in preventing unwantedrotation of the screw 22 and corresponding translation of the wedgestructure 26. This may also aide in allowing the screw 22 to be rotatedin a ratcheting or step-wise manner, with specific detent points. Itshould be noted that a lock-washer or the like could also be used forthis purpose, and that a non-screw-based translation assembly could beused to translate and secure the wedge structure 26, as will be readilyapparent to those of ordinary skill in the art. Each of the plurality ofholding/placement tool recesses 48 includes a lip structure 62 that isselectively engaged by a corresponding hook structure of the tool.

Referring to FIGS. 10 a-10 e, the superior member 12 and the inferiormember include opposing flanges 64 and 66 that fit within thecorresponding cut-away sections 68 and 18 of the inferior member 14 andthe superior member 12, respectively, when the superior member 12 andthe inferior member 14 are nested against one another and/or separatedby a predetermined distance. These opposing flanges 64 and 66 aide inproviding stability to the expandable intervertebral implant 10 bypreventing the superior member 12 and the inferior member 14 fromsliding with respect to one another and the central axis of theexpandable intervertebral implant 10. These figures illustrate that thesuperior member 12 and the inferior member 14 are coupled to oneanother, but allowed to expand away from/contract towards one another,via a pair of “dove-tailed” inserts 70 or the like disposed on eitherside of the expandable intervertebral implant 10 that engage both achannel 72 manufactured into the housing 24 and a channel 74manufactured into the superior member 12 and the inferior member 14. Itwill be readily apparent to those of ordinary skill in the art thatother suitable coupling mechanisms may also be used. In the exemplaryembodiment illustrated, only the portion of the inserts 70 engaging thesuperior member 12 and the inferior member 14 is “dove-tailed,” whilethe portion engaging the housing 24 is not.

FIGS. 11-13 illustrate the “opening” of the expandable intervertebralimplant 10 via rotation of the screw 22 and translation of the wedgestructure 26 towards the housing 24. The constant,substantially-parallel relationship of the superior member 12 and theinferior member 14 should be noted as the wedge structure 26 move alongthe “rails” of the superior member 12 and the inferior member 14.

Referring to FIGS. 14 and 15, in one exemplary embodiment, thecombination placement/deployment tool 76 of the present inventionincludes a pair of elongate arms 78 that each have a hook structure 80on the end that is configured to selectively and releasably engage thecorresponding recess 48 of the housing 24. The combinationplacement/deployment tool 76 also includes a driver 82 disposed betweenthe pair of elongate arms 78 that is configured to selectively andreleasably engage the keyed recess 46 of the screw 22. When rotated, thedriver 82 rotates the screw 22, thereby translating the wedge structure26 (not illustrated) and expanding/contracting the superior member 12and the inferior member 14 of the expandable intervertebral implant 10.

Referring to FIGS. 16 and 17, the combination placement/deployment tool76 further includes a handle 84 for grasping and a socket 86 forattaching a rotating or driver handle 88, such as a ratcheting handle.It will be readily apparent to those of ordinary skill in the art thatthe expandable intervertebral implant of the present invention may beplaced via an open surgical procedure, or via any suitableminimally-invasive portal-type of system.

Referring to FIGS. 18 a, 18 b, 19 a, and 19 b, in an alternativeexemplary embodiment, the present invention provides an expandableintervertebral implant 110 that is selectively disposed in theintervertebral space and deployed, thereby in-situ distracting,realigning, and/or stabilizing or fusing a portion of the spine of apatient in the treatment of injury, disease, and/or degenerativecondition. FIGS. 18 a and 18 b illustrate the expandable intervertebralimplant 110 in an unexpanded, or unactuated, configuration, while FIGS.19 a and 19 b illustrate the expandable intervertebral implant 110 in apartially or wholly expanded, or partially or wholly actuated,configuration. The expandable intervertebral implant 110 again includesa superior member 112 and an inferior member 114, each of which has aproximal ramp portion 113 and 115, respectively, and a distal rampportion 117 and 119, respectively, and a partially or substantiallyconvex or flat opposing surface 121 and 123, respectively, that issuitable for engaging the substantially concave or flat opposingsurfaces of the associated bony superior and inferior intervertebralendplates, once properly prepared. Optionally, the superior member 112and the inferior member 114 are each thinner at the proximal and distalends of the expandable intervertebral implant 110 than they are in thecentral portion of the expandable intervertebral implant 110, such thatinsertion into the intervertebral space may be aided, although this isnot a requirement and the expandable intervertebral implant 110 may havea uniform thickness, when undeployed and/or deployed, from the proximalend to the distal end through the central portion. For similar reasons,the proximal and distal ends of the both the superior member 112 and theinferior member 114 may have a narrowed or rounded shape in anydimension or direction. Once disposed in the intervertebral space, theexpandable intervertebral implant 110 is actuated and deployed, with thesuperior member 112 and the inferior member 114 moving apart from oneanother, while remaining in a substantially parallel and translationallyconstant configuration, seating against the associated intervertebralendplates, and distracting, realigning, and/or stabilizing them to adesired degree. The mechanisms by which this happens are described ingreater detail herein below. This operation is analogous to placing ajack under a car, positioning it appropriately, snugging it in the spacebeneath the car, and then jacking it up. In order to ensure that theexpandable intervertebral implant 110 is held securely in theintervertebral space, the external surface of each of the superiormember 112 and the inferior member 114 is provided with a plurality ofridges 116 or other friction structures, providing purchase with theassociated intervertebral endplates. The overall dimensions of theexpandable intervertebral implant 10 are on the order of severalmillimeters to tens of millimeters, such that a set of implantscontaining a series of incremental implant sizes can provide a heightexpansion range of 7-18 mm or more than 3-5 mm each, for example. Othersuitable dimensions may, of course, be utilized.

When undeployed, the superior member 112 and the inferior member 114 areconfigured such that they nest against and interlock with one another,thereby providing the undeployed expandable intervertebral implant 110with the smallest possible form factor (i.e. the smallest possibleundeployed vertical cross-section and the smallest/shortest possibleundeployed horizontal footprint) for insertion through the skin andmusculature of the patient and into the intervertebral space. Again, themechanisms by which this happens are described in greater detail hereinbelow.

By way of overview, the superior member 112 and the inferior member 114are actuated via the rotation of an actuation bolt 122 disposed throughan internally-bored proximal wedge structure 125 that securely, and in asliding manner, engages the proximal ramp portions 113 and 115 of thesuperior member 112 and the inferior member 114, respectively, at theproximal end of the expandable intervertebral implant 110. Thisactuation bolt 122 is disposed along and through the central axis of theexpandable intervertebral implant 110, between the superior member 112and the inferior member 114. At the distal end of the expandableintervertebral implant, the actuation bolt 122 engages aninternally-threaded distal wedge structure 126 that securely, and in asliding manner, engages the distal ramp portions 117 and 119 of thesuperior member 112 and the inferior member 114, respectively. Theproximal and distal wedge structures 125 and 126 are thereby translatedalong the central axis of the expandable intervertebral implant 110 withrotation of the actuation bolt 122, at least with respect to oneanother. This translation causes the proximal and distal wedgestructures 125 and 126 to interact with the proximal and distal rampportions 113, 115, 117, and 119 of the superior member 112 and theinferior member 114, thereby forcing the superior member 112 and theinferior member 114 apart/together with translation of the proximal anddistal wedge structures 125 and 126. Preferably, the superior member 112and the inferior member 114 each include a nested track structure(described in greater detail herein below), thereby securely couplingthe superior member 112 to the inferior member 114 through the proximaland distal wedge structures 125 and 126. This also allows the trackstructures of the superior member 112 and the inferior member 114 to belonger (versus vertically aligned tracks), thereby permitting the wedgestructures 125 and 126 of a fully contracted (i.e. fully unexpanded)implant 110 to be disposed within the horizontal footprint of thesuperior member 112 and the inferior member 114 while maintainingminimum wedge translation (i.e. travel) length requirements to effectthe required distraction of the implant 110. Again, this makes theassembly as compact as possible, with the smallest possible undeployedvertical cross-section and the smallest/shortest possible undeployedhorizontal footprint. The interaction of the proximal and distal wedgestructures 125 and 126 with the proximal and distal ramp portions 113,115, 117, and 119 of the superior member 112 and the inferior member 114during translation preferably causes the superior member 112 and theinferior member 114 to move apart/together while maintaining asubstantially parallel, translationally constant relationship.Alternatively, the superior member 112 and the inferior member 114 maymove apart with a predetermined lordotic angle. The superior member 112and the inferior member 114 may move apart in a substantially continuousfashion, or they may move apart in 0.5-mm or smaller increments, forexample. In addition, the interaction of the proximal and distal wedgestructures 125 and 126 with the proximal and distal ramp portions 113,115, 117, and 119 of the superior member 112 and the inferior member 114may be designed such that as the superior member 112 and the inferiormember 114 move apart, they also translate with respect to one another.This is helpful in, for example, ensuring that the plurality of ridges116 or other friction structures are securely seated in the bonymaterial.

Another view of the expandable intervertebral implant 110 is provided inFIG. 20. As is evident from FIG. 20, the superior member 112 and theinferior member 114 (not shown here) may each include one or more holes132 or fenestrations to promote bony in-growth and fusion, asappropriate. For example, the expandable intervertebral implant 110 mayinclude a 40 mm² or larger axial graft chamber opening or the like forthe placement of a fusion material.

Referring to FIGS. 21 a and 21 b, preferably, the proximal and distalwedge structures 125 and 126 are disposed within the footprint(s) of thesuperior member 112 and the inferior member 114 in both the fullyunexpanded and fully expanded states—meaning that the expandableintervertebral implant 110 has a known and constant or predictable size,which is a great advantage to an implanting surgeon. The superior member112 and the inferior member 114 each (or collectively) define aninternal space in which the actuation bolt 122 is disposed. This nestingof the actuation bolt 122 within the superior member 112 and theinferior member 114 provides the expandable intervertebral implant 110with the smallest possible form factor when undeployed, allowing thesuperior member 112 and the inferior member 114 to collapse together,without interference from the actuation bolt 122. The proximal wedgestructure 125 has a corresponding bore portion through which theactuation bolt 122 passes, while the distal wedge structure 126 has acorresponding threaded hole portion through which the actuation bolt 122passes. This configuration permits the proximal and distal wedgestructures 125 and 126 to translate smoothly along the central axis ofthe expandable intervertebral implant 110 with rotation of the actuationbolt 122, distracting the superior member 112 and the inferior member114. One or more stabilization members 131 protruding from either orboth of the superior member 112 and/or the inferior member 114 andengaging a corresponding stabilization recess 133 manufactured in theside of the other member 112 or 114 securely hold the superior member112 and the inferior member 114 in a fixed translational alignment andprevent undesirable slipping between the two in any direction, as wellas undesirable rotation or tilting. Thus, the expandable intervertebralimplant 110 will predictably expand upon deployment, as opposed to“clamshelling,” for example.

Referring to FIGS. 22 a, 22 b, 23 a, 23 b, 24 a, 24 b, 25, and 26, inthe exemplary embodiment illustrated, the superior member 112 and theinferior member 114 are essentially mirror images of one another, suchthat manufacturing, inventory, and assembly costs are minimized,although this is not strictly required. Furthermore, in this exemplaryembodiment, the superior member 112 and the inferior member 114 are thesame part, designed to nest with itself when rotated 180 degrees, suchthat manufacturing efficiencies are increased and production andinventory costs are minimized. As described above, one or morestabilization members 131 protruding from either or both of the superiormember 112 and/or the inferior member 114 and engaging a correspondingstabilization recess 133 manufactured in the side of the other member112 or 114 securely hold the superior member 112 and the inferior member114 in a fixed translational alignment and prevent undesirable slippingbetween the two in any direction, as well as undesirable rotation ortilting. Each of the stabilization members 131 includes a horizontalshelf structure 135 manufactured into the interior portion thereof Thishorizontal shelf structure 135 is configured to mate with acorresponding horizontal shelf structure 137 manufactured into anexterior portion of each of the stabilization recesses 133. Togetherthese shelf structures 135 and 137 impart significant stability when thesuperior member 112 and the inferior member 114 are mated, and provide astopping point for collapse of the superior member 112 and the inferiormember 114 together vertically. Each of the proximal ramp portions 113and 115 and the distal ramp portions 117 and 119 of the superior member112 and the inferior member 114, respectively, includes one or moreraised parallel rail structures 128 that run from the central portion ofthe expandable intervertebral implant 110 to the respective end portionof the expandable intervertebral implant 110. These raised parallel railstructures 128 are positioned and configured to engage correspondingrecessed parallel slot structures 130 of the proximal and distal wedgestructures 125 and 126 (see FIGS. 27 a, 27 b, 28 a, 28 b, 29 a, 29 b, 32a, and 32 b). Preferably, each of the rail structures 128 and/or slotstructures 130 includes a lip structure and/or is “dove-tailed” on oneor both sides, such that the rail structures 128 and slot structures 130are allowed to translate with respect to one another, but are preventedfrom disengaging one another all together. The rail structures 128 andslot structures 130 are staggered or offset such that the proximal rampportions 113 and 115 and the distal ramp portions 117 and 119 of thesuperior member 112 and the inferior member 114 and the proximal anddistal wedge structures 125 and 126 are “nested” when assembled, suchthat the form factor (i.e. both the vertical cross-section and thehorizontal footprint) of the expandable intervertebral implant 110 isminimized when undeployed (i.e. unexpanded). This allows the trackstructures of the superior member 112 and the inferior member 114 to belonger (versus vertically aligned tracks), thereby permitting the wedgestructures 125 and 126 of a fully contracted (i.e. fully unexpanded)implant 110 to be disposed within the horizontal footprint of thesuperior member 112 and the inferior member 114 while maintainingminimum wedge translation (i.e. travel) length requirements to effectthe required distraction of the implant 110. Again, this makes theassembly as compact as possible, with the smallest possible undeployedvertical cross-section and the smallest/shortest possible undeployedhorizontal footprint. Again, this also allows the proximal and distalwedge structures 125 and 126 to be disposed within the footprint(s) ofthe superior member 112 and the inferior member 114 in the fullyunexpanded state—meaning that the expandable intervertebral implant 110has a known and constant or predictable size, which is a great advantageto an implanting surgeon. Further, this configuration preserves theintegrity and continuity of the leading (i.e. distal) edge of thesuperior member 112 and the inferior member 114, and allows the proximalramp portions 113 and 115 and the distal ramp portions 117 and 119 to bemade longer, without the rail structures 128 interfering with oneanother, thereby increasing bony surface purchase area.

FIGS. 29 a and 29 b further illustrate the distal wedge structure 126 ofthis alternative embodiment of the expandable intervertebral implant 110of the present invention, highlighting the configuration of the slotstructures 130 and threaded bore 139.

Referring to FIGS. 30 a and 30 b, the superior member 112 includes oneor more downward projecting portions 140 on one side thereof (in theexemplary embodiment illustrated). The inferior member 114 includes oneor more corresponding recesses 142 on one side thereof (in the exemplaryembodiment illustrated). When the expandable intervertebral implant 110is in its collapsed state, these features act as a locking mechanism,increasing implant shear strength and overall stability during deliveryand positioning in the intervertebral space, which may require the useof a slap hammer or other similar striking instrument. Similar lockingtabs 144 and notches 146 may also be used for this purpose in a varietyof configurations.

Referring to FIGS. 31 a and 31 b, the proximal wedge structure 125includes a recessed radial spline 148 (or spiral jaw clutch mechanism)disposed around the central bore 150, such that the expandableintervertebral implant 110 may be expanded in a “ratcheted” manner (i.e.incrementally) and securely hold a given degree of expansion. This“ratcheted” expansion may be reversed for repositioning andredeployment. The recessed nature of the radial spline 148 again reducesthe overall footprint of the expandable intervertebral implant 110,accepting and “hiding” the head portion of the actuation bolt 122.Further, the sides of the proximal wedge structure 125 include grooves152 and recessed pockets 154 that are configured to receive variousgrasping and deployment tools, as described in greater detail hereinbelow.

Referring to FIGS. 33 a and 33 b, the actuation bolt 122 includes acomplimentary radial spline 156 on the back side of the head portion, asmooth shaft portion 158 for passing through the proximal wedgestructure 125, and a threaded portion 160 for engaging the distal wedgestructure 126. This assembly is illustrated in FIG. 34. The head portionof the actuation bolt 122 also includes a keyed recess 162 for receivinga driver, such as a hexalobular driver, by which the actuation bolt 122is rotated to translate the proximal and/or distal wedge structure(s)125 and 126. As is described in greater detail herein below, the driverand holding/placement tool may be incorporated into one assembly, suchthat the expandable intervertebral implant 110 may be grasped,positioned, expanded, and released in a series of simple steps, by asingle surgeon, using a single tool.

Referring to FIGS. 35, 36 a, 36 b, 37 a, 37 b, 38 a, 38 b, 39, 40, 42,43, 44 a, and 44 b, in an alternative exemplary embodiment, thecombination placement/deployment tool 200 of the present inventionincludes a pair of movable elongate arms 202 that each have an interiorretention structure 204 that is configured to selectively and releasablyengage the corresponding recessed pocket 154 of the expandableintervertebral implant 110 in an anti-rotational manner. The combinationplacement/deployment tool 200 also includes a driver disposed betweenthe pair of elongate arms 202 that is configured to selectively andreleasably engage the keyed recess 162 of the actuation bolt 122. Whenrotated, the driver rotates the actuation bolt 122, thereby translatingthe wedge structures 125 and 126 and expanding/contracting the superiormember 112 and the inferior member 114 of the expandable intervertebralimplant 110. The elongate arms 202 are engaged/released via theactuation of a lever mechanism 212 disposed at the opposite end of anelongate shaft 210. The combination placement/deployment tool 200further includes a handle 214 (e.g. an MIS side handle) for grasping anda socket 216 (e.g. a torque limiting handle) for rotating the driver. Itwill be readily apparent to those of ordinary skill in the art that theexpandable intervertebral implant 110 of the present invention may beplaced via an open surgical procedure, or via any suitableminimally-invasive portal-type of system.

As an alternative, FIGS. 41 a and 41 b illustrate a lordotic version ofthe expandable intervertebral implant 310 of the present invention—whichis “thicker” at one end than at the other end, similar to embodimentsdescribed above. This is advantageous for TLIF and ALIF procedures. Sideslope versions may also be produced for DLIF procedures, for example.

Although the expandable intervertebral implant of the present inventionhas been illustrated and described herein with reference to preferredembodiments and specific examples thereof, it will be readily apparentto those of ordinary skill in the art that other embodiments andexamples may perform similar functions and/or achieve like results. Allsuch equivalent embodiments and examples fall within the spirit andscope of the present invention, are contemplated thereby, and areintended to be covered by the following claims.

1. An expandable intervertebral implant, comprising: a superior memberconfigured to engage a superior intervertebral body; an inferior memberconfigured to engage an inferior intervertebral body; and an expansionmechanism disposed between the superior member and the inferior memberconfigured to selectively adjust a separation of the superior memberfrom the inferior member; wherein the expansion mechanism comprises aproximal wedge structure and a distal wedge structure that arerelatively translated between the superior member and the inferiormember, wherein the proximal wedge structure and the distal wedgestructure are each coupled to the superior member and the inferiormember by a plurality of track structures and rail structures.
 2. Theexpandable intervertebral implant of claim 1, wherein one or more trackstructures and rail structures associated with a top surface of thedistal wedge structure are offset horizontally with respect to one ormore track structures and rail structures associated with a bottomsurface of the distal wedge structure.
 3. The expandable intervertebralimplant of claim 1, wherein one or more track structures and railstructures associated with a top surface of the proximal wedge structureare aligned horizontally with respect to one or more track structuresand rail structures associated with a bottom surface of the proximalwedge structure.
 4. The expandable intervertebral implant of claim 1,wherein one or more track structures and rail structures associated witha top surface of the proximal wedge structure are offset horizontallywith respect to one or more track structures and rail structuresassociated with a bottom surface of the proximal wedge structure.
 5. Theexpandable intervertebral implant of claim 1, wherein the expansionmechanism further comprises an actuation bolt that passes through theproximal wedge structure and is coupled to the distal wedge structureand causes the wedge structures to relatively translate when rotated. 6.The expandable intervertebral implant of claim 1, wherein the superiormember and the inferior member each comprise a plurality of rampstructures on their opposed faces.
 7. The expandable intervertebralimplant of claim 6, wherein the superior member comprises a rampstructure that engages the proximal wedge structure and a ramp structurethat engages the distal wedge structure.
 8. The expandableintervertebral implant of claim 6, wherein the inferior member comprisesa ramp structure that engages the proximal wedge structure and a rampstructure that engages the distal wedge structure.
 9. The expandableintervertebral implant of claim 1, further comprising a plurality ofelongate arm structures protruding from the superior member and theinferior member and engaging a corresponding recess of the othercomponent.
 10. A surgical method, comprising: providing an expandableintervertebral implant, comprising: a superior member configured toengage a superior intervertebral body; an inferior member configured toengage an inferior intervertebral body; and an expansion mechanismdisposed between the superior member and the inferior member configuredto selectively adjust a separation of the superior member from theinferior member; wherein the expansion mechanism comprises a proximalwedge structure and a distal wedge structure that are relativelytranslated between the superior member and the inferior member, whereinthe proximal wedge structure and the distal wedge structure are eachcoupled to the superior member and the inferior member by a plurality oftrack structures and rail structures.
 11. The surgical method of claim10, wherein one or more track structures and rail structures associatedwith a top surface of the distal wedge structure are offset horizontallywith respect to one or more track structures and rail structuresassociated with a bottom surface of the distal wedge structure.
 12. Thesurgical method of claim 10, wherein one or more track structures andrail structures associated with a top surface of the proximal wedgestructure are aligned horizontally with respect to one or more trackstructures and rail structures associated with a bottom surface of theproximal wedge structure.
 13. The surgical method of claim 10, whereinone or more track structures and rail structures associated with a topsurface of the proximal wedge structure are offset horizontally withrespect to one or more track structures and rail structures associatedwith a bottom surface of the proximal wedge structure.
 14. The surgicalmethod of claim 10, wherein the expansion mechanism further comprises anactuation bolt that passes through the proximal wedge structure and iscoupled to the distal wedge structure and causes the wedge structures torelatively translate when rotated.
 15. The surgical method of claim 10,wherein the superior member and the inferior member each comprise aplurality of ramp structures on their opposed faces.
 16. The surgicalmethod of claim 15, wherein the superior member comprises a rampstructure that engages the proximal wedge structure and a ramp structurethat engages the distal wedge structure.
 17. The surgical method ofclaim 15, wherein the inferior member comprises a ramp structure thatengages the proximal wedge structure and a ramp structure that engagesthe distal wedge structure.
 18. The surgical method of claim 10, whereinthe expandable intervertebral implant further comprises a plurality ofelongate arm structures protruding from the superior member and theinferior member and engaging a corresponding recess of the othercomponent.